Gemstones, such as diamonds, rubies, emeralds, or sapphires, are valued by observation and measurement of numerous physical characteristics. Perhaps best known are long-established criteria for valuing diamonds. Cut diamonds are valued based on differences in shape, size range, cut, clarity, color, polish, symmetry, fluorescence, finish and light performance. Rough diamonds are valued based on differences in shape, size range, color, clarity, and cut estimate. Diamond value is often also based on the source and reputation of the gemological laboratory providing the grading report for an individual stone.
A variety of gemological laboratories (e.g. American Gem Society (AGS), the Gemological Institute of America (GIA); and Rapaport Laboratories (RAP)) produce grading reports which provide the results of diamond appraisals. Standard grading reports typically indicate the “shape” or “cut” of an appraised gemstone. However standard grading reports are silent regarding how closely the gemstone resembles its purported shape.
Thus a continuing need exists for methods for evaluating the shape of a gemstone.